Drying temperature independent polytetrafluoroethylene

Abstract

The present invention is directed to a product and method of incrementally adding comonomers to co-polytetrafluoroethylene (PTFE) by an improved process, resulting in a PTFE product independent and/or much less dependent upon drying temperatures. The improved PTFE exhibits increased green strength at substantially constant extrusion pressures and an extrusion pressure that is substantially independent of drying temperatures of the wet PTFE.

I claim: 
     
       1. A coagulated dispersion of an extrudable copolymer of tetrafluoroethylene and from 0.03 to 1.0 weight percent of a comonomer selected from the group consisting of perfluoroalkenes, chlorotrifluoroethylene, dichlorodifluoroethylene, hexafluoropropene, perfluoro(n-propyl vinyl ether), perfluoroalkyl trifluoroethylene of 3 to 10 carbon atoms and oxyperfluoroalky trifluoroethylenes of 3 to 10 carbon atoms, characterized by a green strength wherein said green strength is increased with a corresponding extrusion pressure said extrusion pressure remaining substantially constant as a function of drying temperature between about 150 to 250 degrees centigrade. 
     
     
       2. The copolymer of claim 1 wherein said green strength is increased by 20 percent with a corresponding extrusion pressure that remains substantially constant. 
     
     
       3. The copolymer of claim 1 wherein said green strength is increased by 40 percent with a corresponding extrusion pressure that remains substantially constant. 
     
     
       4. The copolymer of claim 1 wherein said green strength is increased by 60 percent with a corresponding extrusion pressure that remains substantially constant. 
     
     
       5. The copolymer of claim 1 wherein said green strength is increased by 80 percent with a corresponding extrusion pressure that remains substantially constant. 
     
     
       6. A coagulated dispersion of an extrudable copolymer of tetrafluoroethylne and from 0.03 to 1.0 weight percent of a comonomer selected from the group consisting of perfluoroalkenes, chlorotrifluoroethylene, dichlorodifluoroethylene, hexafluoropropene, perfluoro(n-propyl vinyl ether), perfluoroalkyl trifluoroethylene of 3 to 10 carbon atoms and oxyperfluoroalky trifluoroethylenes of 3 to 10 carbon atoms, and mixtures thereof, characterized by the independence of said copolymer of the extrusion pressure to drying temperature ratio whereby said ratio comprises an increase in extrusion pressure by 10.6 percent for a 20 degree centigrade increase in drying temperature. 
     
     
       7. The copolymer of claim 6 wherein said copolymer is characterized by the extrusion pressure to drying temperature ratio of less than 8.48 percent increase in extrusion pressure for a 20 degree centigrade increase in drying temperature. 
     
     
       8. The copolymer of claim 6 wherein said copolymer is characterized by the extrusion pressure to drying temperature ratio of less than 6.36 percent increase in extrusion pressure for a 20 degree centigrade increase in drying temperature. 
     
     
       9. The copolymer of claim 6 wherein said copolymer is characterized by the extrusion pressure to drying temperature ratio of less than 4.24 percent increase in extrusion pressure for a 20 degree centigrade increase in drying temperature. 
     
     
       10. The copolymer of claim 6 wherein said copolymer is characterized by the extrusion pressure to drying temperature ratio of less than 2.12 percent increase in extrusion pressure for a 20 degree centigrade increase in drying temperature.